1. Field of the Invention
The present invention relates to a fluorosilicone rubber composition low in swellability in various solvents and good in compression set.
2. Description of the Prior Art
Silicone rubber compositions are excellent in properties such as heat resistance, cold resistance, weather resistance, and electrical resistance properties and are used in various fields. In particular, fluorosilicone compositions having a 3,3,3-trifluoropropyl group in a side chain are excellent also in solvent resistance and are used widely, for example, for diaphragms, 0-rings, and oil seals as parts of transporting apparatuses and parts of petroleum related apparatuses.
However, although conventional known fluorosilicone rubber compositions exhibit excellent solvent resistance to nonpolar solvents such as benzene, they have a problem that they easily swell in polar solvents such as ketones, esters, and alcohols and are poor in solvent resistance to polar solvents. In addition, they are considered to be further improved in fuel oil resistance.
As rubber materials excellent in solvent resistance, fluororubbers are known, but they are defective in that they are, for example, poor in compression set which is important as a property of sealing materials and poor in cold resistance.